Disco Opilioni

As I do every week, I spun the wheel yesterday to find out what the topic for this week's post would be. It told me to write about Cristina. Interesting, I thought, this site doesn't usually focus on early 1980s No Wave performers:

But then, of course, I realised that I'd driven that cheap gag about as far as I could (not very far, as it turned out). The actual topic of today's post is the African harvestman genus Cristina.

Male Cristina armata, from Roewer (1911).

As is not unusual, the harvestman fauna of Africa has been far less extensively studied than that of other continents. Among the long-legged harvestmen, to which Cristina belongs, most known African species belong to the family Phalangiidae, again including Cristina. Two species of Neopilionidae (Neopilio australis and Vibone vetusta) are known from the very south of the continent, and various species of Sclerosomatidae are known from the very north (which, biogeographically speaking, is more part of Europe than Africa, at least as far as harvestmen are concerned). Otherwise, the continent is the preserve of the phalangiids, and Africa is home to the world's only tropical Phalangiidae. What is known of the African phalangiid fauna was mostly reviewed by Staręga (1984).

Cristina is found in eastern African from the Horn south to Mozambique, with an outlying species across the Gulf of Aden in Yemen. Cristina species are also known from central Africa, Ghana and Togo, and it is likely found in a broad band across the entirety of central Africa. Like many other genera of phalangiids, Cristina has transverse rows of spines across the body, but it is distinguished from most confamilials by the presence of four (sometimes two) pairs of denticles or large spines on the eye mound (Cristina crassipes from Togo has the last pair of spines directed backwards and almost looking like a pair of horns). The males have the first pair of legs distinctly swollen in comparison to the remaining legs, but do not have particularly modified chelicerae.

We don't as yet know how the African phalangiids are related to those elsewhere. The Phalangiidae tend, underneath their superficial spines, to be a fairly conservative bunch, and will not reveal themselves easily.

2 comments:

In the strict sense: almost certainly, I would say. There have not been many formal analyses of the group (so far, what few there have been are consistent with monophyly), but the family is quite distinctive. The males have laterally flattened, crochet-hook penes quite unlike those of other harvestmen. What is more of an open question is whether the four subfamilies of Phalangiidae are each monophyletic, as the distinctions between them are not that solidly established.

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The Author

I'm an entomologist and taxonomist, currently based in Perth, Western Australia. If you'd like to comment (or offer work), I can be e-mailed at gerarus at westnet.com.au.Subscribe to Catalogue of Organisms